The present invention generally relates to liquid dispensing apparatus and, more specifically, to liquid dispensing apparatus for dispensing liquids from multiple liquid dispensing modules.
Many manufacturing production lines include one or more liquid dispensing systems for dispensing a liquid onto a continuously moving substrate. Typically, the liquid dispensing system includes a flow metering device providing a pressurized, metered flow of the liquid from a source to a distribution manifold and multiple liquid dispensing modules fluidically coupled with the distribution manifold. Among other variables, the pattern in which the liquid is dispensed onto the substrate is determined in large part by the number and spacing of the liquid dispensing modules.
Certain production lines incorporate liquid dispensing operations that apply a pattern of a heated liquid, such as a hot melt adhesive, to a continuously-moving substrate, such as a woven or non-woven web used in the manufacture of multilayer diapers and other multilayer hygienic products. The multiple liquid dispensing modules are arranged in a spaced array so that hot melt adhesive sprayed from any one of the liquid dispensing modules overlaps the sprays from certain adjacent liquid dispensing modules. Typically, the liquid dispensing modules are clustered so that the pattern of hot melt adhesive is distributed over only selected widths of the continuously moving substrate, such as regions of the substrate near its peripheral edges. Occasionally, the hot melt adhesive is sprayed in an uninterrupted pattern extending between the peripheral edges.
The requirement of a distribution manifold adds significant cost to and reduces the versatility of liquid dispensing systems, such as metering gearhead dispensing systems. As mentioned above, liquid is pumped from a flow metering device through the distribution manifold to the array of liquid dispensing modules. The flow metering device typically includes multiple liquid pumps that provide an individualized stream of liquid to each liquid dispensing module in the array. Each of the liquid streams is dedicated to one of the liquid dispensing modules. To route the liquid streams to the array of liquid dispensing modules, a precisely-spaced set of liquid passageways must be machined in the distribution manifold. Each liquid passageway extends from an inlet on the flow metering device side of the distribution manifold to an outlet on the liquid dispensing module side of the distribution manifold. The outlets are precisely arranged with fixed positions in a spaced array that registers with the spaced array of liquid dispensing modules.
The distribution manifold may also be utilized to distribute other fluids to the liquid dispensing modules. Air passageways for pressurized actuation air must be machined in the distribution manifold for the operation of pneumatically-actuated flow metering devices. Process air, often heated, is used to manipulate the sprays of liquid dispensed from the outlets of the liquid passageways. In liquid dispensing systems that dispense heated liquids such as hot melt adhesives, liquid recirculation passageways must be provided in the distribution manifold to recirculate the heated liquid from outlets of liquid passageways that are blocked in a specific dispensing operation to create a particular spray pattern.
To place the outlets at desired locations, bores creating the liquid and air passageways must be machined with precise inclination angles between two sides of the distribution manifold. The pattern of bores is complex and challenging to design without introducing design errors. When the distribution manifold is machined to form the liquid and air passageways, a machining error can irreversibly damage the distribution manifold. Often, the distribution manifold cannot be remachined to correct such errors and must be discarded.
After the liquid passageways are machined in a particular distribution manifold, that distribution manifold is dedicated to one particular dispensing operation. Certain liquid dispensing systems are used in manufacturing processes having production lines in which the dispensing operation can change, such as those production lines capable of fabricating different products having a range of widths. For example, a single production line may be used to produce diapers from substrates of differing widths to accommodate different diaper sizes. To accomplish product changeovers, the liquid dispensing modules must be repositioned to conform the pattern of dispensed liquid to the differing widths. However, the outlets of the liquid passageways in the distribution manifold cannot be relocated for the purpose of repositioning the liquid dispensing modules. Instead, a different distribution manifold with a differing set of liquid passageways must be provided so that the outlets are arranged with spacings appropriate to the particular dispensing pattern. Therefore, many different varieties of distribution manifolds must be stocked to permit the liquid dispensing system to accommodate a corresponding variety of dispensing patterns.
Another problem associated with changes in the dispensing operation of a liquid dispensing system is that the exchange of one type of distribution manifold with a different type of distribution manifold is time consuming and labor intensive. The dispensing operation must be stopped, the liquid dispensing system must be disassembled and the distribution manifolds exchanged, and then the liquid dispensing system must be reassembled and recalibrated before resuming the dispensing operation. During the exchange, the production line containing the dispensing operation is idle. The cumbersome task of replacing the distribution manifold must be repeated each time the dispensing operation changes. Consequently, the down time and expense associated with product changeovers may be significant and recurring.
Liquid dispensing systems have been proposed that attach a plurality of liquid dispensing modules to individual mounting plates in a manner that permits the mounting plates and associated modules to be individually shifted to a plurality of preset locations relative to each other. One such liquid dispensing system having multiple individually-adjustable liquid dispensing modules is described in U.S. Pat. Nos. 5,683,037 and 5,265,800, both commonly owned by the assignee of the present invention. While these patents disclose effective liquid dispensing systems, a principle disadvantage of such systems is that the fluid connections between the movable plates and a distribution manifold of a flow metering device rely upon oval-shaped polymeric O-rings that seal oval-shaped discharge ports in the manifold. Over time, repeated movements of the movable plates deteriorate the condition of the polymeric O-rings, which are susceptible to wear and to twisting within their respective glands. As a result, the o-rings lose their ability to provide an effective fluid seal. When sealing effectiveness is lost so that leakage occurs, the liquid dispensing operation must be suspended to replace the damaged O-ring.
What is needed, therefore, is a liquid dispensing system having multiple liquid dispensing modules that permits the spacing between adjacent modules to be rapidly adjusted without exchanging one distribution manifold for a different distribution manifold and, for heated liquids, a system that can maintain the liquid at a desired temperature while allowing for the positional adjustment.
The present invention provides an apparatus having multiple liquid dispensing modules for dispensing a liquid, including ambient-temperature liquids and heated liquids, that permits the positions of one or more liquid dispensing modules to be spatially adjusted relative to the positions of adjacent ones of the liquid dispensing modules for altering the pattern of dispensed liquid. In accordance with the principles of the present invention, the apparatus includes a flow metering device having a liquid discharge port operable to discharge metered quantities of a liquid, a stationary plate mounted to the flow metering device, a movable plate mounted for sliding movement relative to the stationary plate, and a liquid dispensing module attached to the movable plate. The stationary plate has a first throughbore extending therethrough and the movable plate includes a liquid passageway with an inlet and an outlet. A liquid dispensing module is fluidically coupled with the outlet of the liquid passageway. The apparatus further includes a liquid supply line having a first end fluidically coupled with the liquid discharge port and a second end extending through the first throughbore in the stationary plate to fluidically couple with the inlet of the liquid passageway. The liquid supply line includes a flexible first portion that permits the liquid discharge port and the inlet of the liquid passageway to remain fluidically coupled when the movable plate is slidingly moved relative to the stationary plate.
In certain embodiments, the apparatus is provided with a heated enclosure that creates a heated space between the liquid discharge port of the flow metering device and the first throughbore of the stationary plate. The heated enclosure includes a first aperture registered with the first throughbore. The heated enclosure is particularly useful for dispensing heated liquids in which the liquid inside each of the plurality of liquid supply lines is maintained in a heated state for dispensing.
In other embodiments, the apparatus includes a flow metering device having a liquid discharge port operable to discharge metered quantities of a liquid, a stationary plate mounted to the flow metering device, a plurality of movable plates each mounted for sliding movement relative to the stationary plate, and a plurality of liquid dispensing modules each attached to one of the movable plates. The stationary plate has a plurality of first throughbores extending therethrough and each movable plate includes at least one liquid passageway with an inlet and an outlet. Each liquid dispensing module is fluidically coupled with the outlet of one of the liquid passageways. The apparatus further includes a plurality of liquid supply lines each having a first end fluidically coupled with one of the liquid discharge ports and a second end extending through one of the first throughbores in the stationary plate to fluidically couple with the inlet of one of the liquid passageways. Each liquid supply line includes having a flexible first portion that permits the liquid discharge ports and the inlet of the interconnected liquid passageway to remain fluidically coupled when respective ones of the movable plates are slidingly moved relative to the stationary plate. The apparatus may be provided with a heated enclosure that creates a heated space between the plurality of liquid discharge ports and the plurality of first throughbores in the stationary plate. The heated enclosure includes a plurality of first apertures each registered with one of the plurality of first throughbores. The heated enclosure is particularly useful for dispensing heated liquids in which the liquid inside each of the plurality of liquid supply lines is maintained in a heated state for dispensing.
Various additional advantages and features of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description taken in conjunction with the accompanying drawings.